How fast a person's heart beats while at rest can predict that person's risk of dying, not only from heart disease but all other causes, say Canadian researchers.
The study, presented today at the Canadian Cardiovascular Congress, found that in people with stable heart disease, the higher their heart rate when they were resting, the higher their risk of death from cardiovascular and all causes.
That was even after the researchers adjusted for all risk factors.
Most normal, healthy adults have a resting heart rate of somewhere between 60 and 100 beats per minute, and a lower resting heart rate is generally better. Someone who's in good physical shape might have a rate in the 50s, while the heart of an elite athlete may need to beat only 40 times per minute.
For this study, Dr. Eva Lonn, a cardiologist and professor at McMaster University in Hamilton, Ont., led a team who reviewed the data from two major clinical studies that followed more than 31,500 patients over four years.
Both studies looked at whether certain medications could lower heart attacks, strokes, and heart failure in older patients with established but stable heart disease.
Dr. Lonn's team decided to use the wealth of data from the studies to study resting heart rate. They found that, compared to heart disease patients with the lowest heart rate (58 beats per minute or less), those with baseline heart rates over 70 beats per minute had:
- a 23 per cent increased risk of having a stroke or heart attack over the four years of study
- a 38 per cent increased risk of dying within four years
They were also more than twice as likely to be hospitalized for heart failure compared with subjects with the lowest heart rate.
The researchers conclude that a higher resting heart rate is a sign of an increased risk for a shorter life expectancy.
"What we can say is the faster the heart rate, the higher the risk. And definitely, an over 70 resting heart rate seems to identify people at increased risk of dying," says Lonn.
It's thought that a low heart rate is less stressful on the blood vessels, and may inhibit cholesterol build-up, thereby lowering the risk of heart attacks and stroke.
Lonn and her co-authors say measuring a patient's resting heart rate is easy to do and, as this study shows, can offer doctors good insight in the health of their heart disease patients, since it's sometimes hard to identify which heart patients are at higher risk than others.
"Heart rate is not sexy. It's not new technology, there's no fancy equipment, but it is a very, very important part of every physical exam," says study co-author Dr. Sherryn Rambihar.
The causes of a fast resting heart rate include smoking, chronic stress and a sedentary lifestyle that involves little physical activity to strengthen the heart.
The good news is that it's possible to slow resting heart rate either with medications to slow the heart or with exercise.
Heart and Stroke Foundation spokesperson Dr. Beth Abramson notes that a high resting heart rate is associated with many conditions that put people at risk, including poorer heart muscle function.
"This study on heart rate is intriguing but it is important that we are reminded how to truly reduce our future risk," she said in a news release.
"Eating a balanced diet, being physically active, managing stress, limiting caffeine intake, and being smoke-free can help improve your heart health, regardless of the effects on heart rate."
